Tapered shunt reed switch

ABSTRACT

A switching device for sensing the position of a displaceable member including a reed switch assembly having a magnet and a pair of contacts within the normal magnetic field of the magnet, the contacts being capable of assuming a circuit closed or opened condition depending upon the flux density of the magnetic field, and further including a magnetic shunt of tapered shape forming part of the displaceable member and insertable different distances into the space between the magnet and the contacts in response to movement of the member in one direction. Means is provided for moving the member in the shunt inserting direction, which movement is opposed by a spring of substantially constant elasticity for the extent of movement of the member.

United States Patent [1 1 Beery TAPERED SHUNT REED SWITCH Inventor: Jack Beery, Farmington, Mich.

Assignee: Burroughs Corporation, Detroit,

Mich.

Filed: Mar. 16, 1972 App]. No.: 235,361

Related US. Application Data Mar. 26, 1974 Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firm-Ralzemond B. Parker; Jerold l. Schneider; Edwin W. Uren 5 7 ABSTRACT A switching device for sensing the position of a displaceable member including a reed switch assembly having a magnet and a pair of contacts within the normal magnetic field of the magnet, the contacts being capable of assuming a circuit closed or opened condition depending upon the flux density of the magnetic field, and further including a magnetic shunt of tapered shape forming part of the displaceable member and insertable different distances into the space between the magnet and the contacts in response to movement of the member in one direction. Means is provided for moving the member in the shunt inserting direction, which movement is opposed by a spring of substantially constant elasticity for the extent of movement of the member.

2 Claims, 8 Drawing Figures l Imm my PAIENIEDmzs m4 sum 1 or 2 PATENTED R26 I974 SHEET 2 OF 2 FIG.5

FIGBA' FIG.6B

TAPERED SHUNT REED SWITCH This is a division of application Ser. No. 52,635, filed July 7, 1970, now abandoned.

BACKGROUND OF THE INVENTION vironment of magnetic ink ribbons as used in printing devices. Therefore, without limiting the meaning of the word ribbon, the invention will be described in this environment. This invention may be utilized when the ribbon is used only once as well as when the ribbon is reusable and also may be utilized when separate supply and take-up reels or spools are used as well as when the supply and take-up'spools are mounted for rotation on a single shaft as in the preferred embodiment. There- I fore the detailed description should be read as merely illustrative of the principles of this invention.

2. Description of the Prior Art When ribbon is fed at a first rate to a take-up spool which is operating at a different or intermittent rate there of, course, repeated variations in the ribbon tension. These variations may result in tangling, stretching, or breaking the ribbon. When a ribbon having a magnetic oxide coating or an ink coating is used, such as in the tape recording and printing arts, excess stretching of the ribbon can cause fragments of the oxide coating or ink coating to break off thereby rendering corresponding portions of the ribbon useless. Prior art solutions to these problems generally provide apparatus designed to maintain the torque developed by the take-up spool drive motor within specific narrow limits that will not damage the ribbon.

Such prior art solutions have utilized either complex circuitry to provide the rapidly responsive take-up spool motor control that is required to restrict the torque, or more modest circuitry which results in a higher cyclic rate of take-up spool operation. The latter type control results in shorter life for the various components.

SUMMARY OF THE INVENTION With these prior art problems in mind it is an object of the present invention to provide means for simply and economically maintaining substantially uniform tension in a ribbon-like member.

It is another object of the present invention to maintain ribbon tension by means of a rapidly responsive control system.

It is yet another object of the present invention to maintain the tension in a ribbon substantially constant within predetermined limits.

It is a further object of the present invention to maintain tension independent of the torque characteristics ofa take-up spool drive motor used for rewinding a ribbon and thus control the maximum diameter of ribbon on a rewind spool.

It is yet another object of the present invention to maximize the life of a read switch that is effectively utilized for controlling a ribbon take-up spool drive motor 2 such that substantially uniform tension in the ribbon is maintained.

These and other objects are accomplished in an apparatus for maintaining tension in a ribbon which is being wound on an intermittently driven take-up spool. A reed switch having a tapered shunt is used to control a motor that drives the take-up spool; the motor being driven intermittently to maintain the ribbon tension substantially constant within predetermined limits. The tapered shunt prevents an excessively rapid recycling of the reed switch, thereby preserving the useful life of the reed switch control.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects of the present invention together with other objects and advantages which may be attained by its use will become apparentupon reading the description of the invention in conjunction with the following drawings. In the drawings wherein like numerals designate corresponding parts:

FIG. 1 is a flow diagram of a ribbon transport system which incorporates the present invention;

FIG. 2 is an elevation view of the ribbon supply and take-up structure of the present invention;

FIG. 3 is a sectional view taken along line 33 of FIG. 2 and includes a portion of the ribbon and utilization device;

FIG. 4 is a side elevation view of a collection line tension mechanism;

FIG. 5 is a plan view of FIG. 4 with various parts broken away;

FIG. 6 comprising FIG. 6A and FIG. 6B is an illustration for comparing operational characteristics of different types of shunts; and

FIG. 7 is a side elevation ofa ribbon level change device.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates the path that a ribbon l1 follows from a supply spool 13 through a drive and utilization apparatus to a take-up spool 15. More specifically the ribbon 11 is assumed to follow a clockwise path from the supply spool 13 through a supply tension apparatus 17, past a utilization device such as printer 19, past a drive wheel or roller 21, through a collection or takeup tension apparatus 23 and over a level changer 25 to take-up spool 15. As the drive wheel or drive roller 21 pulls the ribbon from the supply spool 13 through the printer it simultaneously supplies used ribbon to be rewound on the take-up spool 15; take-up spool 15 being intermittently driven and the take-up tension apparatus 23 maintaining tension in the used ribbon as it is being rewound.

Referring to FIG. 2, a vertically disposed shaft 27 is housed within a freely rotatable sleeve 29. The shaft and sleeve are journaled in a horizontally disposed frame 31. The supply spool 13 is locked onto the sleeve 29 at a first vertical level above the frame 31 and rotates with the sleeve. In -a preferred operation this first vertical level corresponds to that level at which the ribbon is utilized by the printer. In a plane above the supply spool 13, the take-up spool 15 is locked into position on the shaft 27. Preferably the shaft has a slot therein and spool 15 has a key to engage the slot. In a conventional fashion a motor (not shown) drives shaft 27 to rotate the upper or take-up spool 15.

Referring now to FIGS. 2 and 3, the operation of the ribbon supply tension apparatus 17 will be explained. One end of a shaft 33 is journaled in frame 31 and the shaft extends downward from the frame. A triangular plate 35 is disposed below the upper part of the frame 31 and the apex of this triangular plate is rotatably mounted on shaft 33. A pivotable protruding arm 37 is disposed above and pin connected to the right-hand portion of plate 35. A circular indentation 39 in the protruding arm 37 has a radius of curvature equal to that of sleeve 29. The plate 35 is disposed to the left of shaft 27 such that indentation 39 may engage sleeve 29.

As the plate is rotated in a counter-clockwise direction around shaft 33 the indentation 39 engages sleeve 29 to provide a friction brake for stopping the rotation of sleeve 29 and supply spool 13. Arm 37 is urged into frictional engagement with sleeve 29 by a spring 41.

Disposed below triangular plate 35 and also mounted on shaft 33 is a lever 43. Lever 43 is biased or urged by spring 45 in a counterclockwise direction about shaft 33. There is a generally arcuate slot 47 parallel to and adjacent to the base of triangular plate 35. A vertical stud 49 on lever 43 extends upward through slot 47. The free rotational movement of lever 43 is accordingly limited by the engagement of'stud 49 with the ends of slot 47. Once lever 43 and stud 49 are rotated in either a clockwise or counterclockwise direction beyond the point at which the stud contacts a corresponding extremity of slot 47, the lever 43 and the triangular plate 35 will thereafter rotate together as a result of such contact. It is apparent, how'ever, that in the preferred embodiment only clockwise rotation of lever 43 andplate 35 simultaneously is of particular significance since the contact of the indentation 39 of the protruding arm 37 with the sleeve 29 prevents significant counterclockwisc rotation of the triangular plate 35.

At the end of lever 43 opposite to the end mounted on shaft 33 is a pin 51 which extends vertically upward to the level of the supply spool 13. A guide roller 53 is freely spindled on .pin 51 at a level identical to that of the supply spool 13. For convenience in illustration the guide roller is also shown in FIG. 1 however the designation 17 should be thought of as referring to the entire supply ribbon tension apparatus including roller 53.

Considering the operation of the supply tension apparatus generally designated at 17, as the ribbon 11 is fed into the utilization device or printer 19, the pressure on the ribbon from the rotation of roller 21 would be generally clockwise as seen in the view of FIG. '1. This pressure would tend to move the roller 53 to the left causing a generally clockwise rotation of lever 43 against the yielding force of spring 45. When the ribbon tension from the printer exceeds the tension limit, which is defined as the stud 49 reaching one extremity of slot 47, the braking effect of indentation 39 contacting sleeve 29 is released and new ribbon may be drawn from the supply spool 13. This new ribbon would serve to decrease the tension in the ribbon between the area of the ribbon supply spool 13 and the wheel 21; this decrease in ribbon tension permits springs 41 and 45 to urge triangular plate 35 and lever 43, respectively, in a counterclockwise direction back into their biased positions. As this occurs, indentation 39 again engages and stops the rotation of sleeve 29 and supply spool 13. This completes the intermittent ribbon feed or demand ribbon feed cycle.

As a precautionary measure a magnetic flux diverting member 55 may be mounted on the lever 43 between pin 51 and stud 49. This member 55 diverts the magnetic flux from a reed switch 57 mounted on the brakeside of the plate 35 if the lever 43 rotates counterclockwise a predetermined distance. The switch 57 is so positioned that this predetermined rotation occurs only if no ribbon or a broken ribbon is loaded in the system or if the ribbon is not loaded past guide roller 53. If switch 57 is opened by movement of the flux diverting member 55 the entire system should be shut down. Thus switch 57 could be located in the main power line.

As illustrated in FIG. 1, the drive wheel 21 feeds used ribbon from the printer 19 to the take-up spool 15 via the collection line or takc-up line tension mechanism 23. As previously indicated, spool 15 is driven positively by the motor rotating shaft 27. As shown in greater detail in FIGS. 4 and 5, the tension mechanism 23 includes a horizontal frame 59 of non-magnetic material such as aluminum which supports two spindles 61, 61. A cylindrical guide roller 63, 63' is rotatably mounted on each spindle. Disposed through and below the frame 59 in spaced relationship are two vertical cy-' lindrical posts 65, 65' each having a flat bottom thus giving the posts the cross sectional shape of an inverted T. A shunt of magnetic material is slidably mounted on the posts 65, 65 in a plane parallel to and below the frame 59. This shunt includes an elongated rectangular magnetic shunt portion 67, and, at one end, an annular shunt portion 69 of tapered width which gradually decreases as the distance from the rectangular portion thereof increases. The slidable mounting of the shunt is accomplished through two elongated slots 71, 71' formed therein. The slots are arranged to permit the rectangular portion to slide along and rest on posts 65, 65. Near the center of the rectangular portion 67 of the shunt there is a vertically disposed spindle 73. The upper portion of the spindle 73 passes through a slot 75 formed in the frame 59. A guide roller 77 is rotatably mounted on the spindle 73 above the frame 59 at the same vertical level as the fixed rollers 63 and 63' and the drive wheel 21 (FIG. 1). It is to be noted that in the plan view of FIG. 5 the left slot 71, in the partially broken view, is below the level of frame 59, slot75 in frame 59 is shown but right slot 71' is omitted for clarity. However, all three slots are colinear in a plan view.

As the shunt slides in either direction along its elongated slots 71, 71' the spindle 73 and the roller 77 are carried with it. A spring 79 has one end attached to the lower extension of the spindle 73 and the other end attached to a portion of the frame. Spring 79 urges the I shunt and roller 77 to the right as viewed in FIGS. 4 and 5 which is away from the tapered end 69 of the shunt. The urging of spring 79 is resisted by the tension in.the ribbon 11 against the slidable roller 77. If these forces remained in a state of equilibrium the roller 77 would never slide but would remain approximately intermediate the extremities of its slot 75. As the take-up spool 15 and/or the drive wheel 21 operate, however, the length of ribbon 11 between them tends to vary as does the force exerted by the ribbon on the roller. Specifically, as the take-up spool shortens the length of ribbon or as the drive wheel lengthens it, the roller 77 is pulled vby the ribbon 11 and the spring 79 to that physical of' constant elasticity such that contraction or expansion of the spring in the operation of this apparatus is below the elastic limit, then thetension on the ribbon 11 must also remain substantially constant since the spring counteracts all changes in ribbon tension.

To insure that the spring 79 does not function outside the elastic limit, the rotation of the take-up spool 15 is based on movement of the shunt; shunt movement, it will be remembered, corresponds to spring movement. As illustrated in FIGS. 4 and 5, a magnet 81 and a reed switch 83 are disposed near and on opposite sides of the tapered end 69 of the shunt. The flux from magnet 81 affects the reed switch as influenced by the tapered end of the shunt passing between the magnet and the switch. .The contacts of the reed switch 83 are electrically connected in series with a motor or other device which rotates shaft 27 to drive the take-up spool 15. As the roller 77 moves laterally, the tapered end 69 of the magnetic shunt is inserted further into or is further withdrawn from the space between the magnet 81 and the switch 83. When the spring 79 is compressed a predetermined maximum amount, within its constant elasticity range, the'tapered shunt 69 is sufficiently withdrawn .as to correspondingly increase the magnetic field and to maintain the switch contacts closed and the take-up spool 15 rotating. As the spool 15 takesup used ribbon, ribbon tension increases, the spring 79 collection expands and, at the same time, the tapered shunt 69 is inserted in the magnetic field of magnet 81. When the spring'79 has expanded a predetermined maximum amount, sufficient magnetic flux is diverted by the tapered shunt 69 from the tension of the ribbon is reduced and the reed switch contacts to allow them to open. Opening the contacts causes the motor (not shown) to cease rotating shaft 27 and spool 15. Thus ribbon take-up is stopped and this prevents further expansion of the spring 79. As the drive wheel 21 continues to feed ribbon 11 to the coolection apparatus 23 the spring 79 again contracts until the tapered shunt 69 is sufficiently withdrawn from the magnetic field to allow sufficient magnetic flux to affect and close the -switch 83. The shaft 27 and take-up spool are again rotated and the cycle repeats itself as long as the drive wheel 21 continues to feed ribbon 11.

As shown in FIGS. 4 and magnet a second magnet 85 FIG. 6A generally divert a relatively constant amount of flux over their length. That is, the flux density at a reed switch (not shown) will very nearly approach a maximum at all times when the shunt is withdrawn from the magnetic field and a minimum at all times when the shunt is inserted in the magnetic field. The response time of the reed switch is thus a function of the time taken by its flexible contacts to react to the immediate change in a flux density. This reaction time is not constant, and results in zones C (Close) and 0 (Open) along the shunt path during which the contacts may close and open, respectively. Opening or closing of the contacts may occur for any given shunt cycle at any point within the respective open or close zone. The width of the zones shown has been selected purely as a basis for this explanation.

Shunt B, such as is shown in FIG. 63, on the other hand, has a tapered extension 91 which enters the field at its narrow end and widens as the shunt is inserted further. As this shunt enters the field it diverts a gradually increasing amount of flux from the switch contacts, and therefore allows the resiliency of the contacts to predispose the contacts toward an open position. When sufficient flux has been diverted the predisposed contacts open, and the length of the zone of opening,

0, for shunt B is correspondingly smaller than that for contacts is gradually increased and the contacts are predisposed to close when sufficient closure flux is available. Consequently the length of the zone of closand reed switch 87 are mounted along the path of travel of the rectangular portion 67 of the shunt. The second switch and magnet are at the opposite end of the shunt 67 from the tapered end 69. This second switch 87 is so positioned that the rectangular shunt portion 67 interrupts its magnetic field only in the event that no ribbon or a broken ribbon is loaded in the system. This second switch and magnetic also serve as a precautionary device to turn off the entire system in a similar fashion to that described for the supply line tension mechanism switch 57 and shunt 55.

It should be noted that most efficient use of the substantially constant elastic range of the spring 79 may be obtained only if the reed switch 83 reliably opens and closes at the same relative positions of tapered shunt 69 during repeated use. That is, permissive shunt travel must be accurately controlled. This is best explained by reference to FIG. 6A in which a hypothetical shunt A includes only a rectangular portion 89 and to FIG. 6B in which shunt B includes a tapered portion 91 corresponding to the shunt of the present invention. Conventional rectangular shunts such as the type illustrated in ing C, forshunt Bis also smaller than that for shunt A. If distance X, as shown in FIG. 6A, is assumed to be the distance the spring 79 may expand within its constant elastic range, then the maximum shunt travel must also be limited to the distance X. Such a limitation on shunt A results in an appreciably smaller minimum shunt travel, shown as A, than the same limitation applied to shunt B which allows a minimum travel shown as B. Consequently the tapered shunt B offers two primary benefits in that it permits maximum effective use of the constant elastic portion of spring 79 expansion and also insures a maximum time between opening and closure of the reed switch 83, thereby increasing its cycle time. The decrease in switching operations and resulting minimization of energization and de-energization of the motor for the take-up spool 15 thereby result in appreciably a longer life switch 83 and motor life. Optimization of the switch and motor life is primarily a function of the tapered shunt which is varied to suit a given application.

Since the ribbon 11 has been maintained at a constant vertical level throughout the system and the takeup spool 15 is at a higher level, guide means or level change means 25 is provided between the last stationary roller 63 and the take-up spool 15 to change ribbon elevation. Referring to FIG. 7 a rectangular plate 25 is mounted on frame 59 between the last roller 63 of the collection tension mechanism 23 and the take-up spool 15. The width of the plate 25 (perpendicular to the direction of ribbon travel) is greater than the width of the ribbon 11 plus the radius of a full take-up spool 15. This latter requirement prevents the ribbon from slipping off the plate as the outer levels of ribbon are wound on spool 15. The height of the rectangular plate 25 above the frame 59 is such that, the ribbon 11, as it crosses the rectangular plate 25, is at an elevation equal to the horizontal center line 93 of the take-up spool 15. Therefore, as the ribbon 11 passes in contact with the upper edge of the rectangular plate 25 an even wrapping of ribbon about the take up spool 15 is assured. In addition, the top edge of rectangular plate 25 provides a surface about which the ribbon may be twisted 180 so that the inked surface of the ribbon will not be exposed the ribbon is wrapped about the take-up spool 15. Operation Now that the various elements of the system and the operation of the tapered shunt have been described in detail the operation of the entire system will be briefly summarized. I

With the ribbon unwind and rewind system in an I by the roller 53..F rom the drive wheel 21 the ribbon 11 passes to the take-up spool 15 via the collection line tension mechanism 23. The ribbon 11 in this portion of its path is under tension exerted by the biased roller 77. The tapered shunt 69 is fully inserted in the magnetic field of reed switch 83 and the conventional take-up spool drive motor (not shown) is de-energized.

The drive wheel motor is energized by a ribbon demand circuit, not shown, which is related to the printer mechanism. The motor will remain energized until the demand circuit returns to a non-demand state.

Initially, in the portion of the ribbon path between the supply spool 13 and the drive wheel 21, energization of the 'drive wheel motor causes the drive wheel 21 to pull ribbon 11 past the printer 19. As the ribbon is pulled, the tension mechanism roller' 53 moves with lever 43 moving against spring 45 to release the necessary ribbon. Lever 43 rotates to the point at which stud 49 engages the extremity of slot 47 in plate 35. Then, lever 43 and plate 35 rotate together releasing the brake or indentation 39 from sleeve 29. The supply spool 13 freely supplies ribbon 11 to the drive wheel 21 until roller 53, lever 43 and plate 35 have returned to a position at which the brake 39 again engages the supply reel sleeve 29 thus stopping rotation of the supply wheel 21 and the take-up spool 15, energization of the drive wheel 21 causes ribbon 11 to be fed to the takeup spool 15. The roller 77 moves to maintain substantially constant tension on the ribbon 11 and simultaneously whithdraws the tapered shunt 69 from the reed switch 83. Asit is withdrawn the magnetic flux around switch 83 gradually increases until the contacts close. Closure of the switch contacts completes the series connected take-up spool motor circuit and the motor is energized. The take-up spool 15 collects ribbon 11, reversing the lateral motion of the roller 77 and reinserting the shunt 69 in the magnetic field of reed switch 83. The flux affecting the switch 83 is gradually decreased until the contacts open, de-energizing the takeup spool motor and stopping rotation of the take-up spool 15. This energization and de-energization of the take-up reel motor occurs cyclically during energization of drive wheel 21. It should be noted that the intermittent operation of the take-up spool 15 in conjunction with the substantially constant tension maintained on the ribbon 11 by the roller 77 effectively holds the ribbon 11 on the take-up 79. 15 within the upper tension limit of the spring 70. Should the ribbon 11 break at any time, should the ribbon on supply spool come to an end (out of ribbon) or should no ribbon be loaded in the system, the shunt is urged to the right and opens the second reed switch 87 which in turn shuts down the entire system. I

While both the supply 17 and take-up 23 tension mechanisms function cyclically throughout the period of energization of the drive wheel 21, their cycles are entirely independent and the cycle time for each is dependent solely on its respective structural characteristics.

What is claimed is:

1. Apparatus for sensing the position of a displaceable member comprising:

a member shaped to extend essentially in on plane and having at least one end thereof composed of magnetizable material and shaped to form a tapered magnetic shunt,

means mounting the member for rectilinear displacement in the plane of the member and for a limited distance of movement in opposite directions along a straight line path of movement.

means for exerting varying forces on the member tending to move the member in one of said directions along said path of movement,

spring means acting continuously on the member tending to move the samein the opposite direction to that exerted by said force exerting means and having a substantially constant elastic range actionable on the member throughout said distance of movement for continuously applying a substantially constant force opposing that of the force exerting means,

a reed switch device including a magnet and a pair of magnetically influenceable electrical contacts located within the normal range of the magnetic field of said magnet, said pair of contacts being capable of assuming one or the other of two functional conditions depending on the flux density of the magnetic field applied by said magnet and in one case assuming a circuit closed condition and in the other case a circuit opened condition,

said reed switch device being located adjacent to the shunt end of said member and such that the shunt is reversibly movable in the space between the magnet and the pair of electrical contacts in response to the extent and direction of movement of the member by said force exerting means, the tapered formation of the shunt being in the direction of travel of the member and acting to gradually decrease the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the insertable direction relative to the space between the electrical contacts and the magnet thus to cause the contacts to assume one of said two functional conditions and acting to gradually increase the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the withdrawal direction relative to said space thus to cause the contacts to assume the other of said two functional conditions, and

the tapered formation of the shunt cooperating with said range of constant elasticity of the spring means to increase the time period between the open and closing conditions of said pair of contacts thereby increasing the cycle time of the reed switch and decreasing the frequency of its switching operations.

2. Apparatus for sensing the position of a displaceable member comprising;

a member having at least a portion thereof composed of magnetizable material and shaped to form a tapered magnetic shunt,

means mounting the member for limited displacement in opposite directions along a path of movement,

.means for exerting varying forces on the member tending to move the member in one of said directions along said path of movement,

means yieldingly urging movement of the member in the direction opposite to that exerted by said force exerting means and continuously applying a substantially constant force on the member throughout said limited distance of displacement which opposes the forces applied by the force exerting means,

a reed switch device including a magnet and a pair of magnetically influenceable electrical contacts located within the normal range of the magnetic field of said magnet, said pair of contacts being capable of assuming one or the other of two functional conditions depending on the flux density of the magnetic field applied by said magnet and in one case assuming a circuit clo'sed condition and in the other case a circuit opened condition,

said reed switch device being located adjacent to the shunt end of said member and such that the shunt is reversibly movable in the space between the magnet and the pair of electrical contacts in response to the extent and direction of movement of the member by said force exerting means, the tapered formation of the shunt being in the direction of travel of the member to gradually decrease the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the insertable direction relative to the space between the contacts and the magnet thus to cause the contacts to assume one of said two functional conditions and to gradually increase the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the withdrawal direction relative to said space thus to cause the contacts to assume the other of said two functional conditions, and

the tapered formation of the shunt cooperating with the constant force of said yielding means for increasing the time period between the opening and closing conditions of said pair of contacts associated with the reed switch device thereby increasing the cycle time of the reed switch and decreasing the frequency of its switching operations and the energization and de-energization of an electrical load controlled thereby.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 0 5 Dated March 97 Inventor(s) Jack Beery It is certified that efror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 5, line &5, change land magnet a second magnet" to --4 and 5, a second magn0t--. Col. 7, line 56, change "whithdraws" to -withdraws--. Col. 8, line 6, after "take-up" delete "79. line 7, change "spring 70" to --spring 79--,

line 23, change "on plane" to --one plane--.

Signed and I sealed this 24th day of September 1974.

(SEAL) Attest: v

MCCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents ORM (149) USCOMM-DC qoanweo US. GOVIINuINT PRINTING OFFICE! I", O-JS'Jll.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,800,251l Dated March 2 97 Invent0r(s) Jack Beer-y It is certifieo that error appears inthe above-identified patent and that said Letters Patent are hereby corrected as shown below:

C01. 5, line T5, change l and magnet a second magnet" to and 5, a second magnet---. Col. 7', line 56, change "whithdraws" to --withdraws-. Col. 8, line 6, after "take-up" delete "'79.

line 7, change "spring 70" to -spring' 79-, line 23, change "on plane" to -one, plane-.

Signed and: sealed this 24th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents -'ORM PC3-1050 (10-69) USCOMM-DC 6 0316469 t 0.5. GOVERNMENT PRINTING OFFICE: l9 0-365-334, 

1. Apparatus for sensing the position of a displaceable member comprising: a member shaped to extend essentially in on plane and having at least one end thereof composed of magnetizable material and shaped to form a tapered magnetic shunt, means mounting the member for rectilinear displacement in the plane of the member and for a limited distance of movement in opposite directions along a straight line path of movement. means for exerting varying forces on the member tending to move the member in one of said directions along said path of movement, spring means acting continuously on the member tending to move the same in the opposite direction to that exerted by said force exerting means and having a substantially constant elastic range actionable on the member throughout said distance of movement for continuously applying a substantially constant force opposing that of the force exerting means, a reed switch device including a magnet and a pair of magnetically influenceable electrical contacts located within the normal range of the magnetic field of said magnet, said pair of contacts being capable of assuming one or the other of two functional conditions depending on the flux density of the magnetic field applied by said magnet and in one case assuming a circuit closed condition and in the other case a circuit opened condition, said reed switch device being located adjacent to the shunt end of said member and such that the shunt is reversibly movable in the space between the magnet and the pair of electrical contacts in response to the extent and direction of movement of the member by said force exerting means, the tapered formation of the shunt being in the direction of travel of the member and acting to gradually decrease the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the insertable direction relative to the space between the electrical contacts and the magnet thus to cause the contacts to assume one of said two functional conditions and acting to gradually increase the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the withdrawal direction relative to said space thus to cause the contacts to assume the other of said two functional conditions, and the tapered formation of the shunt cooperating with said range of constant elasticity of the spring means to increase the time period between the open and closing conditions of said pair of contacts thereby increasing the cycle time of the reed switch and decreasing the frequency of its switching operations.
 2. Apparatus for sensing the position of a displaceable member comprising: a member having at least a portion thereof composed of magnetizable material and shaped to form a tapered magnetic shunt, means mounting the member for limited displacement in opposite directions along a path of movement, means for exerting varying forces on the member tending to move the member in one of said directions along said path of movement, means yieldingly urging movement of the member in the direction opposite to that exerted by said force exerting means and continuously applying a substantially constant force on the member throughout said limited distance of displacement which opposes the forces applied by the force exerting means, a reed switch device including a magnet and a pair of magnetically influenceable electrical contacts located within the normal range of the magnetic field of said magnet, said pair of contacts being capable of assuming one or the other of two functional conditions depending on the flux density of the magnetic field applied by said magnet and in one case assuming a circuit closed condition and in the other case a circuit opened condition, said reed switch device being located adjacent to the shunt end of said member and such that the shunt is reversibly movable in the space between the magnet and the pair of electrical contacts in response to the extent and direction of movement of the member by said force exerting means, the tapered formation of the shunt being in the direction of travel of the member to gradually decrease the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the insertable direction relative to the space between the contacts and the magnet thus to cause the contacts to assume one of said two functional conditions and to gradually increase the flux density of the magnetic field applied to the pair of electrical contacts as the shunt is moved in the withdrawal direction relative to said space thus to cause the contacts to assume the other of said two functional conditions, and the tapered formation of the shunt cooperating with the constant force of said yielding means for increasing the time period between the opening and closing conditions of said pair of contacts associated with the reed switch device thereby increasing the cycle time of the reed switch and decreasing the frequency of its switching operations and the energization and de-energization of an electrical load controlled thereby. 